Methods and apparatus for cryo-therapy

ABSTRACT

Methods and apparatus for cryo-therapy are disclosed herein. This includes a hollow guidewire disposed within a catheter having helical loops contacting tissue. A coolant delivery tube disposed within can have a coolant delivered from a proximal end into the guidewire lumen. The coolant flows back proximally through the guidewire while cooling the guidewire surface and cooling or cryogenically ablating the contacting tissue. To minimize guidewire exposure to surrounding fluids or tissue, insulative barriers can be attached to the guidewire. A coolant delivery tube and return lumen can be integrated from a single extrusion in various configurations. Expandable balloons can also be used to expand the loops of the guidewire to contact the tissue. Also, helical loops with a coolant delivery tube or stem disposed longitudinally within the loops can be used and the loops can also have a variable collapsible cooling region.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional PatentApplication No. 60/350,177, entitled “Methods and Apparatus forCryo-Therapy” filed Nov. 2, 2001, and U.S. patent application Ser. No.10/010,399, entitled “Methods and Apparatus for Cryo-Therapy” filed Dec.5, 2001.

TECHNICAL FIELD OF THE INVENTION

The present invention relates to cryo-therapy. More particularly, thepresent invention relates to methods and apparatus for endovascularlycooling and/or freezing preselected regions of tissue.

BACKGROUND ART OF THE INVENTION

Acute ischemic syndromes involving arterial blood vessels, such asmycardial infarction, or heart attack, and stroke, frequently occur whenatherosclerotic plaque ruptures, triggering the formation of bloodclots, or thrombosis. Plaque that is inflamed is particularly unstableand vulnerable to disruption, with potentially devastating consequences.Therefore, there is a strong need to detect and locate this type ofplaque so that treatment can be initiated before the plaque undergoesdisruption and induces subsequent life-threatening clotting.

Researchers, acting on the theory that inflammation is a factor in thedevelopment of atherosclerosis, have discovered that local variations oftemperature along arterial walls can indicate the presence of inflamedplaque. The temperature at the site of inflammation, i.e., the unstableplaque, is elevated relative to adjacent plaque-free arterial walls.

Using a tiny thermal sensor at the end of a catheter, the temperature atmultiple locations along an arterial wall were measured in people withand without atherosclerotic arteries. In people free of heart disease,the temperature was substantially homogeneous wherever measured: anaverage of 0.65° F. (0.36° C.) above the oral temperature. In peoplewith stable angina, the temperature of their plaques averaged 0.19° F.(0.11° C.) above the temperature of their unaffected artery walls. Theaverage temperature increase in people with unstable angina was 1.23° F.(0.68° C.). The increase was 2.65° F. (1.47° C.) in people who had justsuffered a heart attack. Furthermore, temperature variation at differentpoints at the plaque site itself was found to be greatest in people whohad just had a heart attack. There was progressively less variation inpeople with unstable angina and stable angina.

The temperature heterogeneity discussed above can be exploited to detectand locate inflamed, unstable plaque through the use of cavity wallprofiling apparatus. Once located, treatment can then be initiated uponthe inflamed, unstable plaque region.

One such method of treatment involves cryo-therapy in which regions oftissue may be cooled to temperatures as low as −112° F. (−80° C.) bycatheters inserted endovascularly into a patient. This form of treatmentdelivers energy to ablate the tissue in a manner which is generallysafer and more effective than other conventional methods of treatment.

Various conventional endovascular catheters used for freezing, heating,or ablating tissue are well known. Certain catheters used for coolingand/or freezing typically employ one of several methods. One such methodtakes advantage of cooling by use of a phase change refrigerant whichmay enter a patient's body at ambient temperature and attains cooling byexpansion within a cooling chamber disposed within the catheter bodylocated at the selected treatment site. The wall of the cooling chamberis typically placed in contact with adjacent tissue to effect conductioncooling or ablation.

Another method involves utilizing the expansion of a phase change orhigh pressure coolant exiting from a nozzle within the catheter tip tocreate a highly turbulent flow region.

However, problems exist with conventional cooling and cryo-treatmentdevices. One such problem is that conventional devices usually exert anundue amount of force on the region of interest. If the region ofinterest cannot withstand these forces, it may be damaged. The insidewalls of a healthy human artery are vulnerable to such damage.Furthermore, if inflamed, unstable plaque is present it may be rupturedby such forces.

Another problem with conventional devices is that they can only treattissue at one specific location. In order to treat an entire tissueregion of interest, one would need to move the cooling apparatus fromlocation to location. If the cooling apparatus were placed on anangioplasty balloon, for instance, the balloon would need to bedeflated, placed at the desired location, inflated and placed in contactwith the tissue, and cooled, and so on for each treatment location. Thiscan be very tedious, can increase the risk of damaging the vessel wallor rupturing vulnerable plaque, and may not treat the entire region oftissue.

Accordingly, there exists a need for a device which is able tocryogenically treat a predetermined region of tissue, such as a regionof unstable plaque, efficiently and effectively without damaging thesurrounding and underlying tissue.

SUMMARY OF THE INVENTION

Cryo-therapy of tissue involves many different device variations andmethods. One variation involves having a hollow ablating tool or ahollow guidewire configured to form multiple loosely spaced helicalloops. The guidewire itself may be formed of a thin wire wound intosmall helical coils of a predetermined diameter that may lie tightlyadjacent to one another forming a central passageway. The guidewire mayhave a first straightened configuration when constrained within acatheter and a second relaxed configuration self-forming or springinginto the helical loops upon being removed from the catheter.Accordingly, the guidewire may be made of a material such as springsteel or a superelastic alloy with shape memory characteristics, e.g.,nitinol.

In this variation, the device may be advanced to a region of tissue tobe cryogenically treated and the helical loops may be withdrawn toradially extend into contact with the targeted tissue. Within the hollowguidewire, a coolant delivery tube may be disposed to extend entirely tothe distal end of the guidewire or near the distal end. Alternatively,the coolant delivery tube may be anchored to the distal end of theguidewire. Within the delivery tube, a coolant or refrigerant may bepumped from a proximal end, either by a positive or negative pressurepump and regulator located proximally. The delivered coolant may passinto the guidewire lumen through one or multiple delivery ports definedalong the delivery tube surface at or near the delivery tube distal end.Once the coolant passes into the guidewire lumen, it may travelproximally through the guidewire while cooling the guidewire surface andsubsequently cooling or cryogenically ablating the contacting tissue.

After the desired tissue has been treated, the guidewire may bewithdrawn into the catheter and the catheter assembly moved to the nexttreatment site. Alternatively, the guidewire may be slowly withdrawninto the catheter while the catheter is held stationary relative to thetissue; the guidewire in this case may cool or ablate the tissue whilein motion, i.e., while being deployed or withdrawn.

The tip or cap of the guidewire may be made of a thermally conductivematerial, such as stainless steel or nitinol, to effect a specifiedcontacting region for treatment of the tissue. Also, a lining or elasticmembrane capable of withstanding low temperatures may be disposed overthe guidewire, either within the guidewire lumen or on an outer surfaceof the guidewire to help contain the coolant within the device. Therefrigerant or coolant used may be in either liquid or gas form and mayinclude a number of different chemicals and compounds such as nitrogen,nitrous oxide, carbon dioxide, chilled saline, fluorinated hydrocarbon(Fluorinert™), and liquid chlorodifluoromethane, among others.

Alternatively, a coolant having a low boiling point may be used to allowdelivery through a delivery tube in a liquid form. Once this coolant ispumped into the guidewire lumen, by virtue of the heat transferred fromthe surrounding tissue, blood, or fluid around the guidewire, the liquidcoolant may undergo a phase transition into a gas and subsequently bepumped back proximally through the guidewire lumen while cooling theguidewire. Another alternative is to pass the coolant through a valvelocated at the distal end of the delivery tube. As the coolant passesthrough the valve, it expands into a cooling gas by what is known as theJoule-Thompson effect. Fluids such as nitrogen, nitrous oxide, or cardondioxide may be suitable for such a mode of heat transfer.

To minimize the exposure of the guidewire to blood, fluids, or othertissue, insulative barriers or shingles may be attached to at least aportion of the loops to help insulate the guidewire. Reducing the heattransfer area of the guidewire to tissue or blood not being treated mayaid in optimizing the efficiency of the coolant during treatment.

Different variations on the guidewire itself may be utilized toefficiently cool or ablate tissue. For instance, a guidewire may haveboth a coolant delivery tube and expansion or coolant return lumenintegrated from a single extrusion. Alternatively, separate deliverytubes may be integrated with a coolant expansion/return lumen to form anintegral tubular structure. Other variations may include having acentral coolant delivery lumen surrounded by a plurality of insulatingand coolant return lumens. Conduction members may optionally be embeddedinto the wall of the guidewire such that the conduction members contactthe coolant to effect a thermal circuit for optimal heat transfer.

Different modes of deployment may also be utilized. The guidewire maysimply be withdrawn from the catheter and left to self-form or radiallyextend until it contacts the tissue walls. But expansion devices such asexpandable balloons, e.g., angioplasty balloons, may be utilized byplacing one within the loops of the guidewire and expanding it to movethe loops of the guidewire into contact with the tissue. Once contact isachieved, the balloon may be deflated and removed from the area. Also,the helical loops of a guidewire may also be integrally formed in, e.g.,a bilayered balloon having an integrated return channel or lumen for thespent coolant to pass through. Such an expandable balloon preferably hasa throughpath or flowthrough channel which would allow blood or otherfluids to continue flowing uninterrupted through the vasculature.

Furthermore, self-forming helical loops may also be utilized with acoolant delivery tube or stem disposed longitudinally within the loops.This device may be rotatably withdrawn or advanced through a catheter asa unit and may facilitate placement of the device upon the region oftissue to be treated. And other variations also may be used which have avariable collapsible cooling region. Such a cooling region may bemanipulated at its proximal end to concentrate or disperse the heattransfer area contacting the targeted tissue depending upon the desiredmode of treatment.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a cryo-therapy device positioned within an arterial bloodvessel with several helical guidewire loops deployed.

FIG. 2 shows a representative side view of a variation of thecryo-therapy device with the guidewire partially withdrawn.

FIG. 3A shows a detailed cross-sectional side view of a variation on theguidewire distal end.

FIG. 3B shows a detailed cross-sectional side view of another variationon the guidewire distal end.

FIG. 3C shows cross-section 3C-3C of the variation from FIG. 3B.

FIG. 3D shows a detailed cross-sectional side view of another variationon the guidewire distal end.

FIG. 3E shows a detailed cross-sectional side view of yet anothervariation on the guidewire distal end having variable coolant deliveryports.

FIG. 4 shows a variation on the cryo-therapy device having insulativebarriers attached to the guidewire.

FIG. 5A shows an isometric view of a representative section of avariation on the tubing for delivering coolant.

FIG. 5B shows a longitudinal cross-section of the interior of the tubingfrom FIG. 5A.

FIG. 6 shows another variation on the tubing for delivering coolant.

FIG. 7 shows a cross-sectioned view of another variation on the tubingfor delivering coolant.

FIG. 8 shows a cross-sectioned view of yet another variation on thetubing for delivering coolant.

FIG. 9 shows a cross-sectioned side view of a partially withdrawnguidewire contacting a region of tissue to be treated.

FIGS. 10A to 10C show a variation on the deployment of a cryo-therapydevice within a vessel using an angioplasty balloon.

FIG. 11 shows a variation on the cryo-therapy device in which thecoolant delivery tube is helically disposed within an expandablebilayered balloon.

FIG. 12 shows another variation on the cryo-therapy device in which thecoolant delivery tube is disposed within an expandable balloon havingembedded conduction contacts.

FIG. 13 shows a representative cross-section of a variation on thecryo-therapy device having an expandable flowthrough balloon.

FIG. 14 shows another variation on the cryo-therapy device in which thehelical loops are in fluid communication with a translatable androtatable coolant delivery stem.

FIGS. 15A and 15B show yet another variation on the cryo-therapy devicein which an expandable balloon may be disposed within the guidewirelumen prior to deployment.

FIG. 16 shows yet another variation on the cryo-therapy device in whichthe helically looped guidewire may be longitudinally variable.

DETAILED DESCRIPTION OF THE INVENTION

Cryogenic treatment of tissue may involve many different devicevariations and methods. As shown in FIG. 1, cryo-therapy device 10 isshown positioned within arterial blood vessel 12, which has its wallpartially removed for clarity. One variation of the device 10 is shownas having a hollow guidewire 20 configured to form multiple looselyspaced helical loops 22. Guidewire 20 is preferably made of a thin wirewhich may be wound into small helical coils of a predetermined diameterthat may lie tightly adjacent to one another to form a hollow guidewire20 defining a central passageway. These loops 22 may be held withinlumened catheter 18 in a first configuration while being delivered tothe desired treatment site.

Once ejected or pushed from catheter 18, guidewire 20 may beself-deploying or self-forming such that when it is unconstrained, itreconfigures itself into a second configuration. This may beaccomplished by having guidewire 20 self-form or spring into helicalloops 22 upon being removed from catheter 18 or guidewire 20 may forminto helical loops 22 upon exposure to the vessel 12 environment.Accordingly, guidewire 20 may be formed from a metal such as springsteel that can be deformed into a first straight configuration to springinto a second looped configuration when withdrawn from catheter 18.Guidewire 20 may alternatively be made from a superelastic metal, suchas nitinol, which may automatically form into the looped configurationfrom a straight one upon withdrawal from catheter 18. Furthermore,guidewire 20 may also be made from a superelastic metal, again such asnitinol having shape memory alloy characteristics. Thus, guidewire 20may be initially inserted through catheter 18 at an initial lowertemperature, e.g., by injecting cold saline solution over guidewire 20.Upon withdrawal from catheter 18 within the body lumen of vessel 12, theambient heat from the surrounding environment such as the blood ortissue may transform guidewire 20 into helical loops 22.

Guidewire 20 may also be made from a composite such as a nitinol tubedisposed within the guidewire structure. In this manner, the martensiticor superelastic properties of nitinol may be combined with spring steelcharacteristics. Guidewire 20 may also be made from other biocompatiblematerials such as copper, constantan, chromel, or alumel.

As further seen in FIG. 1, once guidewire 20 is withdrawn from catheter18, the helical loops 22 preferably reconfigure themselves such thatthey extend radially to come into gentle contact with the inner wall orendothelium 14 of vessel 12. Helical loops 22 are preferably positionedwithin vessel 12 such that they come into contact with a location of thetissue to be treated, such as plaque 16. Once the desired region oftreatment, such as plaque 16, is contacted or in close proximity toguidewire 20, the cryogenic treatment may be effected by cryotherapydevice 10. After the desired tissue has been treated, guidewire 20 maybe withdrawn and catheter 18 may be moved to the next treatment site.Alternatively, guidewire 20 may be slowly withdrawn into catheter 18while catheter 18 is held stationary relative to the tissue; guidewire20 in this case may cool or ablate the tissue while in motion, i.e.,while being deployed or withdrawn.

Variations of the guidewire 20 as well as various methods and devicesfor sensing and measuring characteristics of regions of tissue, such asplaque 16, are discussed in further detail in each of the following U.S.patent applications. Each application is currently co-pending, have allbeen filed on Jul. 12, 2001, and are all incorporated herein byreference in their entirety: U.S. patent application Ser. No. 09/904,012entitled “Expandable Device for Sensing Temperature Profile of a HollowBody Organ”; U.S. patent application Ser. No. 09/904,080 entitled“Method for Sensing Temperature Profile of a Hollow Body Organ”; U.S.patent application Ser. No. 09/904,212 entitled “Device for SensingTemperature Profile of a Hollow Body Organ”; U.S. patent applicationSer. No. 09/904,024 entitled “Method for Sensing and Mapping TemperatureProfile of a Hollow Body Organ”; U.S. patent application Ser. No.09/903,960 entitled “Method for Mapping Temperature Profile of a HollowBody Organ”; U.S. patent application Ser. No. 09/904,220 entitled“Expandable Device for Mapping Temperature Profile of a Hollow BodyOrgan”.

FIG. 2 shows a close-up representation of guidewire 20 partiallywithdrawn from catheter 18. Guidewire 20 has been partially extendedfrom catheter 18 through lumen 30. Catheter 18 may have multiple accesslumens through which a variety of devices, e.g., temperature profilingdevices, optical devices, etc., may be accessible, although a singlelumen 30 is presently shown. The guidewire distal end 32 is shownpartially removed for clarity to reveal a variation of the coolingstructure. As seen, guidewire 20 may be formed by wound wire 36 suchthat guidewire lumen 34 is defined within. A cap or tip 38 may be placedat the distal end of guidewire 20 to cover guidewire lumen 34 and may bemade of a variety of biocompatible conductive materials, such asstainless steel or nitinol. Cap 38 may also be made of a variety ofpolymeric materials capable of withstanding low temperatures.

In this variation, coolant delivery tube 40 may be placed at leastpartially within guidewire lumen 34. Tube 40 preferably extendsthroughout the length of lumen 34 such that the distal end 54 ofdelivery tube 40 is just proximal of cap 38. A lining or elasticmembrane 44 may be formed to cover the inner surface of wire 36 and heldby, e.g., an adhesive 45, to ensure that coolants or refrigerantsflowing within guidewire 20 are fully contained within. Membrane 44 maybe made of various materials capable of withstanding low temperatures,e.g., silicone, polyethylene (PE), fluoroplastics such aspolytetrafluoroethylene (PTFE), fluorinated ethylene polymer (FEP),perfluoroalkoxy (PFA), and thermoplastic polymers, such as polyurethane(PU), etc. The distal section of delivery tube 40 may have at least onedelivery ports 42 and preferably a number of ports 42 spaced along thedistal length. A refrigerant or coolant may be pumped from a proximalend of delivery tube 40 down to its distal end such that the coolantpasses through delivery ports 42 near the guidewire distal end 32. Thecoolant pumped into guidewire lumen 34 through delivery ports 42 maythen be channeled back through to the proximal end of guidewire 20 andcatheter 18 meanwhile cryogenically cooling the guidewire 20 surfacewhich subsequently cools or ablates the targeted tissue which guidewire20 contacts. Delivery tube 40 may be inserted into guidewire lumen 34and deployed within vessel 12 either with guidewire 20 or it may beinserted separately into lumen 34 after guidewire 20 has already beendeployed. Accordingly, lumen 34 may be used for other purposes as well,e.g., holding a temperature sensing device for measuring the temperatureof the wall of vessel 12 prior to the cryogenic treatment.

To regulate the coolant pumped through device 10, a regulator (notshown) connected to the proximal end of device 10 may be used to controlthe amount of pressure within the coil. A positive pressure pump may beused to deliver the coolant through device 10 via tube 40, but anegative pressure pump may also be used to draw the coolant throughguidewire lumen 34. Use of negative pressure may also aid in ensuringthat excess coolant does not escape into a patient's body if a leak orfailure in the structure of guidewire 20 were to ever occur.

The refrigerant or coolant used may variously be in liquid, gas, ormixed form and may include a number of different chemicals and compoundssuch as nitrogen, nitrous oxide, carbon dioxide, chilled saline,Fluorinert™, and liquid chlorodifluoromethane, among others.Alternatively, a coolant having a low boiling point may be used to allowdelivery through tube 40 in liquid form. Once this coolant is pumpedinto guidewire lumen 34, by virtue of the heat transferred from thesurrounding tissue, blood, or fluid around guidewire 20 and/or by therapid expansion of the coolant, the liquid coolant may undergo a phasetransition into a gas and subsequently be pumped back proximally throughlumen 34 while cooling guidewire 20. The coolant may also be passedthrough a valve 51 located at the distal end of delivery tube 40. As thecoolant passes through valve 51, it may expand into a cooling gas bywhat is known as the Joule-Thompson effect and this gas may be used tocool the device and ablate the tissue. Temperatures which may be used toeffect the desired results may be as low as 14° F. to 41° F. (−10° C. to5° C.), or even lower. Fluids such as nitrogen or nitrous oxide may besuitable for such a mode of heat transfer. Accordingly, tube 40 ispreferably formed of a metal or polymeric material capable ofwithstanding extremely low temperatures. Such materials may includemetals such as nitinol and stainless steel, as well as polymers such assilicone, PE, PTFE, FEP, PFA, and thermoplastic polymers, such as PU,etc.

To determine the preferable flow rates of the coolant through guidewire20 to have effective cooling and tissue treatment, as well as the amountof heat transfer necessary for cooling the tissue, a standard equationfor calculating convective heat transfer from the tissue may be used.The equation (1) is shown below:q _(c) =h _(c) A(T ₁ −T ₂)   (1)where, q_(c)=the heat transferred from the contacting tissue; h_(c)=theconvection heat transfer coefficient; A=the surface area the coolant isexposed to; T₁ and T₂ represent the temperature differences through thevarious media which the heat is transferred.

Various methods of coolant delivery may be employed. For instance, FIG.3A shows one variation of a detailed cross-sectional view of guidewiredistal end 32 from FIG. 2. As seen, delivery tube 40 may be disposedwithin guidewire lumen 34 such that the delivery tube distal end 54 islocated in apposition to cap 38. As coolant is pumped in 50 through tube40, it may optionally pass through delivery ports 42 and/or deliverytube distal end 54. The coolant flow 52 may then be passed proximallyback through guidewire lumen 34. For a given device, such as that shownin FIG. 2 as device 10, the coolant flowing through delivery tube 40 mayhave a flow rate of about 40 cm³/min. (cc/min.) to drop the temperatureto an effective level for treatment. As coolant 52 passes over membrane44 and wire 36, coolant 52 becomes spent while transferring heat andlowering the temperature of wire 36. Cap 38 may also be made ofthermally conductive materials such as biocompatible metals likestainless steels. A thermally conductive cap 38 may aid in cooling thecap 38 temperature to allow for direct or selective tissue ablation viacap 38. Delivery tube 40 may also be selectively placed within guidewirelumen 34 such that cooling of selective portions of guidewire 20 occurswhere the delivery tube distal end 54 is located.

Another variation on the guidewire distal end 32 is seen in FIGS. 3B and3C. FIG. 3B shows a cross-sectioned side view of an alternative coolantdelivery method. An anchored coolant delivery tube 55 may be disposedwithin lumen 34 of guidewire 20. Delivery tube 55 may have an anchoringend 56 which may be formed integrally with anchoring cap 38′ or by avariety of other methods. Having anchoring end 56 formed with cap 38′may facilitate the cooling of cap 38′ if coolant is channeled throughtube 55. Delivery tube 55 may be formed of a polymeric tube capable ofwithstanding low temperatures for extended periods of time.Alternatively, tube 55 may be formed of wound wire strands 57 forming ahollow central lumen through which the coolant may be delivered, as seenin FIG. 3C which is the cross-section 3C-3C taken from FIG. 3B. Coolantmay be delivered through delivery ports 42 such that the coolantcontacts wire 36 and is passed proximally through guidewire lumen 34subsequently cooling the guidewire 20 as the coolant passes through.

FIG. 3D shows another variation on the guidewire distal end 32. Asshown, an elastic membrane or coating 58 may be applied exteriorly ofwound wire 36. Membrane 58 is preferably made of any of the polymericmaterials described above which are capable of withstanding lowtemperatures and may be placed exteriorly of wire 36 to aid with thelubricity of the device as well as containing the coolant withinguidewire lumen 34. In this variation, coolant delivery tube 61 may bedisposed within guidewire lumen 34 such that coolant 50 deliveredtherethrough would exit the tube 61 distal end, as shown by exitingcoolant 52, at expansion region 59 and preferably in contact withexpanded cap 38″. In this variation, expanded cap 38″ may be made of athermally conductive material, e.g., stainless steel, such that coolingmay be facilitated and cap 38″ may be used for selective tissue contactand ablation. Although delivery tube 61 is shown with coolant 52 exitingthe distal tip portion to expand in expansion region 59 and effectivelycool cap 38″, tube 61 may also have delivery ports defined in its wallsas in the other variations described above.

FIG. 3E shows yet another variation on the guidewire distal end 32. Thisvariation is similar to that shown in FIG. 3A, but coolant delivery tube63 may have delivery ports of variable sizes and diameters. As shown,delivery ports 65 located closer towards the proximal end of deliverytube 63 may have diameters which are relatively smaller than thediameters of distally located delivery ports 67. The farther distallydelivery ports 67 are located, the larger they may become in diameterrelative to proximal delivery ports 65 to aid in the distribution ofpassing coolant 52 under even pressure throughout the guidewire.

Measures may be taken to optimize the heat transfer between the tissueand the guidewire while minimizing heat transfer to other parts of thebody during treatment. As seen in the cross-section of FIG. 4, hollowguidewire 20 with coolant delivery tube 40 disposed within is shownwithdrawn from catheter 18 and forming helical loops 22 in contact withinner wall 64 of vessel 12. While loops 22 are in contact with vesselwall 64, the contacted area may be ablated by the cooled loops 22.However, the blood 60 flowing past the loops 22 may also be cooled,thereby reducing the efficiency of the coolant in ablating the tissuesince the heat transfer is occurring over a larger area of the loops 22.Thus, insulative barriers or shingles 62 may be attached to a portion ofthe loops 22 facing the blood flow 60. Barriers 62 may be attached overthe entire exposed loops 22 facing the blood flow 60, as shown, or overportions of loops 22 and may be made of a variety of compressible,thermally insulative materials preferably deliverable through a catheter18. Such materials may include any of the polymers described above,e.g., silicone, polyethylene (PE), fluoroplastics such aspolytetrafluoroethylene (PTFE), fluorinated ethylene polymer (FEP),perfluoroalkoxy (PFA), and thermoplastic polymers, such as polyurethane(PU), etc.

Other variations of the guidewire coil itself may be used to delivercoolants and refrigerants therethrough. Rather than having a separatecoolant delivery tube disposed within a hollow guidewire coil, avariation of the guidewire coil shown in FIGS. 5A and 5B mayalternatively be used. As seen in FIG. 5A, the wire used to form thehollow guidewire may itself be formed from a single extrusion shown inthe representative section of delivery tube 70. Such a tube may be madeof a variety of materials capable of withstanding low temperatures,e.g., stainless steel, nitinol, etc. Alternatively, a slightly largerversion of the integral delivery tube 70 may be formed directly into thehelical loops. In either case, such a tube 70 is preferably asingle-piece tube having a coolant lumen 72 and an expansion lumen 76formed integrally within tube wall 74.

FIG. 5B shows a longitudinally cross-sectioned view of the interior ofintegral delivery tube 70. Coolant delivery ports 78 defined alongcoolant lumen 72 may place coolant lumen 72 in fluid communication withexpansion lumen 76. In operation, coolant delivered through lumen 72 maypass or expand through delivery ports 78 into expansion lumen 76, wherethe larger surface area may be utilized to effect a more efficient heattransfer. Delivery ports 78 may be positioned at predetermined locationsalong coolant lumen 72 such that when tube 70 is formed into helicalloops, the contact between tube 70 and the desired region of tissue fortreatment is optimized.

FIG. 6 shows another variation of the guidewire coil in the isometricview of a section of tube 80. In this variation, tube 80 may be formedover separate integral delivery tubes 82 formed within tube wall 84.Delivery tubes 82 may be formed from separately extruded wires or tubesand then tubing wall 84 may be formed with delivery tubes 82. As above,delivery tubes 82 may be used to deliver coolant for expansion and/orreturn through expansion/return lumen 86. Alternatively, delivery tubes82 may be used to complete a circuit of delivered and returning spentcoolant while lumen 86 may be used as an access channel for otherapplications and devices. Separate expansion lumen 86 is preferablyformed integrally within tube 80 in this variation.

Another alternative variation for a guidewire coil is shown in FIG. 7.Here, a representative cross-section of guidewire 90 is seen havingcoolant 94 delivered through coolant delivery lumen 92. There may be anynumber of additional lumens 96 having smaller diameters than lumen 92and surrounding delivery lumen 92, as shown. Guidewire 90 in thisvariation may be extruded to form an integral wire or tubing having thenumber of different channels. Additional lumens 96 may be filled withair or they may be evacuated to provide additional insulation as coolant94 is delivered through guidewire 90. The coolant may be channeled backto the proximal end of guidewire 90 by any number of coolant returnlines 98, which may be located within at least some of lumens 96 or thecoolant may be channeled back directly within lumens 96. As the coolantis returned to the proximal end of guidewire 90, cooling at the distalend and along the outer surface of the guidewire 90 may be effected totreat contacting tissue, as described above.

FIG. 8 shows another variation for a guidewire coil in therepresentative cross-section of guidewire 100. As shown, guidewire 100may have a coolant delivery lumen 102 for transporting coolant 104within. There may be any predetermined number of heat transfer channels106 radially disposed around and in fluid communication with deliverylumen 102 through corresponding coolant channels 108. Channels 106 maybe located along the length of guidewire 100 at selected locations tooptimize the heat transfer at specified locations. As coolant isdelivered through delivery lumen 102, it may enter heat transferchannels 106. A conduction member 112 may be embedded within wall 110such that it contacts the coolant in channels 106 to transfer heat fromthe outer surface of guidewire 100 to or from the coolant containedwithin channels 106 to effect ablation. Conduction member 112 ispreferably a biocompatible and thermally conductive material such asstainless steel, nitinol, etc. Also, member 112 may be formed in variousconfigurations such as curves, straight lines, etc. over the outersurface of guidewire 100 depending upon the desired range of contactwith the surrounding tissue and the area to be cooled or ablated.

FIG. 9 shows a variation of device 10 in operation. As shown, thecross-sectioned guidewire 20 is partially withdrawn from catheter 18 andis reconfigured to a helical configuration within vessel 12, which isalso cross-sectioned for clarity. As guidewire 20 reconfigures itself,it may contact the targeted region for treatment, in this case, unstableplaque 16. Guidewire 20 may gently contact plaque 16 at contact region120, as shown. Once the targeted area of tissue is contacted, coolantmay be delivered through delivery tube 40 disposed within guidewirelumen 34. As the coolant passes through delivery ports 42 and/ordelivery tube distal end 54, it may flow proximally through guidewirelumen 34 while cooling the guidewire 20, cap 38, and contacted plaque 16at contact region 120. The tissue at region 120 may be ablated by thecooled guidewire 20 by keeping the temperature between about 35° to 77°F. (20 to 25° C.) for a period of about 1 to 25 minutes. The use of ahelically looped guidewire for cooling the tissue allows for the bloodflow to remain relatively uninterrupted within the vessel 12 during thetreatment time.

An alternative deployment method may include the use of angioplastyballoons, as seen in FIGS. 10A to 10C, particularly for vessels whichmay have a relatively wide diameter. FIG. 10A shows cryotherapy device130 positioned within vessel 12 with hollow guidewire 132 deployed andreconfigured into helical loops 134. To facilitate extending loops 134radially, an expandable balloon, e.g., angioplasty balloon 138, may beintroduced into vessel 12 and inbetween loops 134. Balloon 138 may beintroduced separately via another catheter, or it may be introducedthrough the same catheter through which guidewire 132 is introduced.Once positioned within loops 134, balloon 138 may be expanded slowly tofurther radially extend loops 134 until they gently contact inner wall14 of vessel 12, as seen in FIG. 10B. During the expansion of balloon138, blood flow 136 through vessel 12 may be occluded temporarily untilballoon 138 is collapsed. Once loops 134 are in gentle contact withinner wall 14, balloon 138 may be removed and treatment to the tissuemay occur, as described above. FIG. 10C shows loops 134 contacting innerwall 14 with blood flow 136 resumed.

Another variation for deploying a helically-shaped coolant delivery tubeis shown in FIG. 11. This variation employs a bilayered expandableballoon 140 having a helically wound coolant delivery tube 142 disposedwithin a helical coolant return channel 144. Coolant delivery tube 142preferably releases coolant near the tube distal end 146 throughdelivery ports 148 which flows back proximally towards balloon proximalend 150 through return channel 144 and through coolant return lumen 152.During deployment, balloon 140 may be in a deflated state until it ispositioned at the tissue to be treated. Balloon 140 may then be inflatedsuch that return channel 144 contacts the tissue and coolant may bepumped into delivery tube 142 such that the tissue contacting balloon140 is cooled or ablated. It may be desirable to maintain blood flowthrough the vessel in which balloon 140 is treating tissue, thus athroughpath 154 may be defined through balloon 140 to facilitate such ablood or fluid flow path when balloon 140 is in an expanded state.

In addition to the expandable balloon 140 in FIG. 11, another variationon an expandable balloon 160 is seen in FIG. 12. Balloon 160 may alsodefine a throughpath 162 throughout the device for facilitating blood orfluid flow through the balloon 160 for when it is in an expanded statewithin a vessel lumen. This variation shows coolant delivery tube 164disposed within balloon 160. Any number of conduction contacts 170 maybe embedded within the surface of balloon 160 to effect optimalconductive heat transfer. Contacts 170 are preferably made of abiocompatible metal which is thermally conductive, e.g., stainlesssteel, nitinol, etc. When coolant is pumped into the balloon 160 throughcoolant ports 166, the coolant may spread throughout balloon 160 andthermally conduct heat through contacts 170 from the contacting tissuewall before being drawn through coolant return lumen 168.

FIG. 13 shows a representative cross section of one variation on anexpandable flowthrough balloon 180 which may be used with a number ofvariations. Balloon 180 is shown in cross section disposed within vessel12. This variation may have an expandable membrane configured to expandin at least two directions. A coolant delivery tube 190 may be locatedwithin the expandable membrane which may be made of thinned membranes182 for contacting vessel 12 and insulative membranes 184 which mayinsulate the coolant from blood and fluids passing through flow channel194. As coolant is passed through delivery tube 190, the coolant mayflow through delivery ports 192 and expand into expansion region 186. Asmore coolant flows into region 186, the membrane may expand and contactvessel 12 at thinned membranes 182 creating conductive regions 188.Although this variation shows two apposed expanding regions, any numberof expandable areas may be implemented depending upon the desired effectand area for cooling.

A further variation on having a helically shaped cooling guidewire orcoil is shown in FIG. 14. Delivery catheter 200 may have a rotatablecoolant delivery stem 202 which may be withdrawn from lumen 206. Anumber of helically wound loops 204 in fluid communication with a distalend of delivery stem 202 may wind about stem 202 to transport coolantback towards a proximal end of catheter 200. In operation, catheter 200may be advanced within a vessel to a treatment site. Both stem 202 andloops 204 may be withdrawn from catheter 206 and loops 204 may beallowed to extend radially so that they come into contact with thetissue. Coolant may then be delivered through delivery stem 202 and backthrough loops 204 to effect treatment to the tissue contacting loops204, as described above. Stem 202 and loops 204 may be independentlyrotatable and translatable relative to catheter 200 to enable effectiveplacement of the device. Once treatment is concluded, stem 202 and loops204 may be withdrawn back into catheter lumen 206 and removed from theregion.

Another variation on an expandable balloon is shown in FIGS. 15A and15B. This variation may be disposed at the end of any of the helicallywound guidewires described above to effect localized treatment at thedistal end of the guidewire. Alternatively, this variation may also beutilized independently to cool or ablate tissue. FIG. 15A shows hollowguidewire 210 having an everted and deflated balloon 216 withdrawnproximally within guidewire lumen 214 and creating recessed cavity 218.The end of balloon membrane 216 is preferably attached to guidewirewalls 212 at balloon attachment region 224. Coolant delivery tube 222may be seen attached at its distal end to the end of balloon membrane216 at attachment point 220. After guidewire 210 is radially extendedinto helical loops and is adjacent to the region of tissue to betreated, as described above, stem 222 may be advanced distally.Advancing stem 222 forces balloon membrane 216 to evert because ofattachment point 220 and withdraws membrane 216 from recessed cavity218. Once balloon membrane 216 has been extended, coolant may bedelivered through stem 222 and passed through delivery ports 226 intoballoon membrane 216. The coolant may then force balloon membrane 216 toexpand, as shown in FIG. 15B, causing membrane 216 to contact the tissuewall for treatment. The spent coolant may then return proximally throughreturn channel 228.

FIG. 16 shows another variation in which the helically looped guidewiremay be longitudinally variable. Collapsible guidewire device 230 isshown as having coolant delivery tube 234 disposed within guidewire 232,as in some of the other variations above. A portion of guidewire 232 maybe partially insulated with insulation 236 and control member 238 may bepositioned longitudinally within the loops of guidewire 232. The distalend of member 238 may be attached to the distal tip of guidewire 232 atattachment point 240. Control member 238 may be a wire or stiff memberand is preferably manipulated at its proximal end to move guidewire 232in the direction of movement shown by arrow 244 to variably collapse orexpand device 230 longitudinally. This variability in longitudinallycontracting or expanding device 230 creates a collapsible region 242 inwhich the loops of guidewire 232 may be concentrated or dispersed tocontrol the heat transfer area contacting the targeted tissue.

The applications of the cryo-therapy devices discussed above are notlimited to endovascular treatments but may include any number of furthertreatment applications. Other treatment sites may include areas orregions of the body such as organ bodies or spaces between the bodycavity. Modification of the above-described assemblies and methods forcarrying out the invention, and variations of aspects of the inventionthat are obvious to those of skill in the art are intended to be withinthe scope of the claims.

1. An apparatus for thermally treating a hollow body organ comprising: acatheter having a proximal end and a distal end and defining at leastone lumen therebetween; a guidewire defining at least one passagewaytherein, wherein the guidewire is configured to have a firstconfiguration when disposed within the lumen and a second radiallyextended configuration when withdrawn from the lumen; and a deliverytube disposable within the guidewire passageway for transporting afluid, wherein the delivery tube defines at least one exit port near adistal end of the delivery tube through which the fluid passes.
 2. Theapparatus of claim 1 further comprising a cap disposed over a distal endof the guidewire.
 3. The apparatus of claim 2 wherein the cap comprisesa thermally conductive material.
 4. The apparatus of claim 1 furthercomprising a membrane disposed along the guidewire passageway forcontaining a coolant flowing therethrough.
 5. The apparatus of claim 1further comprising a plurality of insulative barriers attached to anouter surface of the guidewire.
 6. The apparatus of claim 1 furthercomprising an elongate control member having a proximal end and a distalend, wherein the distal end of the control member is attached to adistal end of the guidewire such that the guidewire is manipulatablealong a longitudinal axis defined by the catheter via a proximal end ofthe elongate member.
 7. The apparatus of claim 1 wherein the guidewireis configured to self-form from the first configuration to the secondlarger configuration.
 8. The apparatus of claim 1 wherein the guidewirecomprises a superelastic metal.
 9. The apparatus of claim 1 wherein thesecond configuration comprises a plurality of helical loops configuredto extend radially into contact with the hollow body organ.
 10. Theapparatus of claim 1 wherein the delivery tube defines a plurality ofadditional exit ports near the distal end.
 11. The apparatus of claim 10wherein each of the additional exit ports has a diameter which increasesin size the farther distally the exit port is located.
 12. The apparatusof claim 1 wherein the delivery tube further comprises a valvepositioned at the exit port.
 13. The apparatus of claim 1 wherein thedelivery tube distal end is anchored at a distal end of the guidewire.14. The apparatus of claim 1 wherein the delivery tube is integrallyformed within the guidewire passageway.
 15. The apparatus of claim 1wherein the fluid comprises a liquid or gas coolant.
 16. The apparatusof claim 15 wherein the fluid comprises a coolant selected from thegroup consisting of nitrogen, nitrous oxide, carbon dioxide, saline,fluorinated hydrocarbon, and chlorodifluoromethane.
 17. The apparatus ofclaim 1 wherein the fluid is in a liquid phase in the delivery tube andin a gaseous phase when passed through the exit port.
 18. The apparatusof claim 1 further comprising a pump in fluid communication with thedelivery tube at a proximal end of the tube.
 19. An apparatus forthermally treating a hollow body organ comprising: a catheter having aproximal end and a distal end and defining at least one lumentherebetween; an expandable balloon attached to the distal end of thecatheter, a surface of the balloon defining at least one helicalpassageway therein; and a delivery tube disposable within the helicalpassageway for transporting a fluid, wherein the delivery tube definesat least one exit port near a distal end of the delivery tube throughwhich the fluid passes.
 20. The apparatus of claim 19 wherein theballoon defines a channel longitudinally therethrough when the balloonis in an expanded stated.
 21. The apparatus of claim 19 wherein thedelivery tube defines a plurality of additional exit ports near thedistal end.
 22. The apparatus of claim 21 wherein each of the additionalexit ports has a diameter which increases in size the farther distallythe exit port is located.
 23. The apparatus of claim 19 wherein thefluid comprises a liquid or gas coolant.
 24. The apparatus of claim 23wherein the fluid comprises a coolant selected from the group consistingof nitrogen, nitrous oxide, carbon dioxide, saline, fluorinatedhydrocarbon, and chlorodifluoromethane.
 25. The apparatus of claim 19wherein the fluid is in a liquid phase in the delivery tube and in agaseous phase when passed through the exit port.
 26. The apparatus ofclaim 19 further comprising a pump in fluid communication with thedelivery tube at a proximal end of the tube.
 27. A method of thermallytreating a hollow body organ comprising: advancing a catheter within thehollow body organ to a region of tissue to be treated; extruding aguidewire from the catheter and allowing the guidewire to radiallyextend into contact with the region of tissue, wherein the guidewiredefines at least one passageway therein; flowing a fluid through adelivery tube, wherein the tube is disposed within the passageway suchthat the fluid passes through at least one exit port defined near adistal end of the tube and flows within the passageway; and thermallytreating the region of tissue in contact with the guidewire via thefluid flowing within the passageway.
 28. The method of claim 27 whereinthe guidewire radially extends by self-forming from a firstconfiguration into a pre-formed second larger configuration whenextruded from the catheter.
 29. The method of claim 27 wherein theguidewire is comprised of a superelastic metal.
 30. The method of claim28 wherein the second configuration comprises a plurality of helicalloops.
 31. The method of claim 30 wherein the guidewire is radiallyextended by an expandable balloon placed within the helical loops. 32.The method of claim 27 wherein the fluid comprises a liquid or gascoolant.
 33. The method of claim 32 wherein the fluid comprises acoolant selected from the group consisting of nitrogen, nitrous oxide,carbon dioxide, saline, fluorinated hydrocarbon, andchlorodifluoromethane.
 34. The method of claim 27 wherein the fluid ispassed through a valve positioned at the exit port.
 35. The method ofclaim 34 wherein the fluid is in a liquid phase in the delivery tube andin a gaseous phase when passed through the exit port.